Spiral filament



Nov. 23, 1943. c v, LIT TQNv I 2,334,716

SPIRAL FI LAMENT Filed Jan so, 1943 uvwszvro amass u urr .AZ'TM onic efliciency.

Patented Nov. 23, 1943 v H C -1 72 45X This invention. relates-to improvementsinspiral and, more particularly to filaments filaments.

builtup from a pluralityof spiral-windings and adapted for use in vacuum tubes andother-electron or-he'at-emittingdevicesi r An object of thisinvention is to provide a novel improvedifilament'structure. 1 Anotherobject of this invention is toprcvide a multi-spiral filament structure having relatively high longitudinal rigidity permitting sm'all' s pacingbetween'wiresi-i. r

- .A iurther object of; this inventionrig'tog provide wire 32;

other while a' -scuice of power such a's' I 1 and half" r: the one bifilar 'wiriding consisting-6r almulti spirahfilament having. thei'advantagessot relatively low filamentzcurrent, but. high. thermi,

Otherobj ects' and advantages of the present invention will become more apparent from a study of the following description of a preferredQem-y bodiment of my invention'illustrated in the" ac 7 companying drawing, in which: I I

Fig. 1 is a vertical plan view of a preferred form of filament structure in accordance with the present invention, showing. the surrounding tube structure partially broken away and partially in section;

Fig. 2 is a top end view of the filament illustrated in Fig. l. v

In a preferred form of the present invention,

such as illustrated in the drawing, the composite filament is made up of a pair of bifilar windings.

' One bifilar'winding may consist of two wires such as 3! and 32 which are connected together at their top, with their end leads extending down- .ward, longitudinally of the filament. The second bifilar winding is made up of separate'windings 33 and 34 likewise connected together at the top.

The two windings are interwound and separately the -Wire 3|, will then; flow upwardly thiou'gh th' wire' 33 of the second bifilar winiiiiigi-andg-ther'ia downwardly through the wire 34'; I By providing. a-icurrentfiow which is inopposite directions in'. adj acent :filamentl turns, the possibility of ih duced electromagnetic currnt 'as a result ofrcur rent flow in the windings isobviated the neu tralizing' action of? adjacent turns: In order to place 'theentirefilamentstructure at gr ound p'o tentia-l withi irespect' ito g'radiorfrequencyicurrents,

' all 'four-Sfilamentqleads asiwell as the supportin cases additional supports will be 7 rods may be grounded through suitable condensers 50..

I Whi1e the specific form of invention illustrated is directed to. a quadrifila'r filament formed from two bifilar windings, the principles of the invention are applicable to other filaments containing more than two'sets of bifilar windings. In such additional bifilar winding, while the inter-connection between all the bifilar windings willstill be such as to provideopposite current flow in adsupported by rods 35 and 36. In the preferred ar-' rangement illustrated, the rods 35 and 36 are provided at one end with slots 40 and 42 respectively which receive the end connections of the two bifilar windings, which may also be welded into the slots to secure rigidity and a good electrical connection. i

The ends of the two bifilar windings as well as the lower ends of the supporting rods may pass through a glass seal 44 to which may be connected the remaining portion 46 of a tube envelope.

' The leads of the bifilar Winding are preferably.

interconnected with one another either inside or outside of the tube so that the current in adjacent turns of the filament as a whole flows in opposite directions. In Fig. 1, for example, the leads of the windings 3| and 33 are connected to one anjacent wires. 7 'All of the windings'as well as the supports may be grounded with respect to high frequency currents by the inclusion of suitable condensers.

The invention described above'will satisfy the objects primarily stated. The resulting filament structure will have a more uniform emission area and greater strength and rigidity than the same length'of Wire in one coil, while at the same time it has less volume than a pluralityof unnested parallel or series coils. The magnetic and electrostatic effects of the filament are minimized.

And while I have described above the principles of my invention in connection with certain specific structure, it is to be clearly understood that this description is made only by way of example and not as a limitation on the scope. of my invention as setforth in the objectsand the accompanying claims. a

I claim:

1. A spiral filament structure for vacuum tubes and the like, comprising a plurality of substantially identical coaxial bifilar spiral windings threaded one within the other and with their respective common ends lying substantially within a single plane, and a. supporting rod for each I o een 48 for heatin'g the filament is connec'te'd acfoss thewir es 32 and 34.; "Accordingly.- it' will bese'eh l that current flowing fron'rthe positive'tei niinail' c-fthe battery 4 l will flowl pwardlythrbugh tiie ill returndownwardly through the secprovided foreach a 5.1'Ihe combin bifllar winding mounted within the windings and each'rod being connected to the common end of its respective winding.

2. A filament structure in which the distance between the wires of each bifllar winding is equal to the distance between turns of the spiral filament as awhole.

according to claim, 1,

8. A quadrifilar spiral filament comprising a pair of substantially identical bifilar spiral windings, each bifilar winding consisting of a single wire wound with double, spaced turns joined at one end and having longitudinally extending leads projecting from its other end, and means for coaxially mounting said bifilar windings,

3. 'A spiral filament structure for vacuum tubes i s and the likeycom prisinga plurality of substan'- tially identicarbiillar spiral windings; eachbi-' fllarl windingucon'sisting of a single wire wound with double, spaced turns joined at one end and from its 1 other end, and means, for coaxially mounting said biiilar windings, screwed one with in the other and with theirjoinedends'all'sube,

' stantially within a common plane, saidmea'ns" comprising a supporting ,rod fer Jeac'hi. bifilar I screwed one within the other and with their joined ends both substantially within a common plane, said means comprising a pair of supporting V rods extending longitudinally within the composite filament, each rod having a slot at one end having longitudinally extending leads projecting adapted to receive the joined end of one of the I V windings winding extending longitudinally :within' the.

windings, each rod being connected atone end" I to the; joined section of its respective winding filamentstructure according to claim ,3, in

which the distance between'fthe .wires of each )bifllar winding is equal to the distancebetween turns' oi the spiral filament as a whole; l

' tionaccording to claim 3, in

- syrne combination according to claim 8', in fwhichlthe distance between the wires of each bifilar winding is equal to one-fourth the distance between the'turns of that winding.

10. ;The combination according to claim 8, in combination with means for serially connecting said bifilar windings so that the current fiow in the composite-spiral filament is in opposite directions in adj acent' turns;

which thelone end of each rod is provided with n,

' itransverse slot for receiving the joined end of its f supportingwihding, 3 I

=6, The combination according to claim: 3, a combination with'meansfor serially, connecting the, composite spiral filament is inopposite direc- ,tions inadjacent turns; v. V a a I 7,.-Thecombinationraccording 'to claim- ,3;fin? combination with means for capacitatively icon- 7 1 said bifi1ar; windings1sothatlthecurrent flow in 7 tion ,in

ll. {The combination 'accorcling to claim 8, in combination with means forscapacitatively. cou+ pling the: endslof each vbifilar winding and. the other jencls oi each supporting rod to ground.

" 112. The combination according toclaim V8,.in

ccmbinationwith means for, serially connecting "said bifilarl windings so thatrthe' current flowlin the composite'spiral filament is in opposite direcadjacent turns, andmeans for capacita- .j tively 'coupling the ends of each bifllar winding and itheaother ends .of each supporting rod to pling the ends I of each lbifilar" winding and :the I other ends oteach supportingrrod to ground. H 

